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    <meta charset="UTF-8">
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    <title>Document</title>
</head>
<body>
    <script>
        Array.prototype.max = function(){
            return Math.max(...this)
        }
        
        let arr = [1,2,3,4,5]
        let arr2 = [1,2,3,4,5,6,7,8]
        const maxNum = arr.max()
        console.log(maxNum);
        Array.prototype.sum = function(){
            return this.reduce((total,current)=>total + current)
        }
        const sum = arr2.sum()
        console.log('arr2sum:'+arr2.sum());
    </script>
</body>
</html>